This invention relates to a fixing device and an image forming apparatus using the fixing device.
A fixing device is used in an image forming apparatus such as a printer, a facsimile or the like. The fixing device applies heat and pressure to a printing medium to which a toner image has been transferred, so that the toner image is fixed to the printing medium. A type of fixing device (i.e., a heat roller type) has a heat roller, and another type of fixing device (i.e., a belt type) has a heat transferring belt. In these fixing devices, a release agent is applied to the surface of the heat roller or the heat transferring belt, in order to prevent the toner from sticking to the surface of the heat roller or the heat transferring belt. An example of the fixing device is discloses in, for example, Japanese Laid-Open Patent Publication NO. 2003-98884 (particularly, Page 3 and FIG. 1).
Recently, the image forming apparatus is required to be adaptable to a borderless printing, i.e., a printing without leaving a blank margin on the perimeter of the printing medium. However, if the margin on the leading edge of the printing medium in the feeding direction of the printing medium is small, there is a possibility that the printing medium may not separate from the heat roller or the like and may be wound around the heat roller or the like. Thus, a sufficient margin needs to be left on the leading edge of the printing medium, and therefore the borderless printing is not enabled. Further, in order to easily separate the printing medium from the heat roller, it is necessary to apply a large amount of release agent to the heat roller. However, in such a case, a large amount of release agent may adhere to the surface of the printing medium, with the result that the printing quality may be degraded.